1. Field of the Invention
This invention relates to copyholders, specifically to an improved line-guide advancement mechanism for a copyholder.
2. Discussion of Prior Art
This invention was the subject matter of Patent Office Disclosure Document No. 268967 filed Dec. 10, 1990.
Heretofore, line-guide advancement mechanisms for copyholders have had various operational and structural disadvantages which limited their usefulness and commercial viability. The copyholder having an integral line-guide advancement mechanism is already known as it is disclosed in U.S. Pat. No. 375,425 to Parkinson & Locke (1887). Several other attempts have been made to design line-guide advancement mechanisms that are simple, compact, reliable, easy to use and commercially feasible. As the cited reference Patents show, many useful improvements in the design of line-guide advancement mechanisms have been recognized; however, none of these have achieved their common purpose: to become an essential part of the daily lives of those persons whose activities include transcribing information from written, typed or printed documents.
All of the line-guide advancement mechanisms heretofore known suffer from some or all of a number of disadvantages:
(a) The mechanism used to cause and control line-guide advancement is complex, requiring a multiplicity of contiguous items to produce a simple, step-wise movement.
(b) The operator's control oftentimes requires the use of one or more hand actions away from the transcribing apparatus during transcription thereby reducing operator efficiency.
(c) The mechanism used offers a limited range of spacing selection in the step-wise movement of the line-guide or offers only a discrete set of spacings. Either of these choices limits the mechanism's usefullness over the wide disparity of line spacings encountered in written, typed and printed documents.
(d) Their manufacture requires extensive machine tool set-ups and, even when manufactured in cost-effective lot sizes, carry a heavy economic burden.
(e) The assembly, alignment, proof testing and maintenance of the total assembleage are labor intensive and require mechanical skills beyond those which can be expected in the average user.
(f) All cited references rely upon a copy-holding frame or platen which forms an integral portion of the line-guide advancement mechanism. Without this integral frame or platen, the mechanism cannot perform its intended function.